Insert an LDAP login module similar to this at the end of the security-modules portion of the file, just before
</security-modules>:
<module name="LDAP Login Module">
<role-mapping modRole="sybase" uafRole="uaAnonymous,uaPluginAdmin,sccUserRole" />
<role-mapping modRole="administrators" uafRole="uaAnonymous,sccAdminRole" />
</module>